add net/setsockopt

[zevv]

This PR adds the net/setsockopt function to src/core/net.c; this allows a number of common socket options to be configured to support broadcast and multicast traffic on sockets. Additional options can later be added when needed.

Example for receiving mdns packets:

(def sock (net/listen "0.0.0.0" "5353" :datagram))
(net/setsockopt sock :so_broadcast true)
(net/setsockopt sock :ip_add_membership "224.0.0.251")
(net/setsockopt sock :ip_multicast_ttl 255)
(pp (net/read sock 512))

What is the appropriate error behavior for:

• Passing wrong options (currently panics)
• the setsockopt() call failing (currently panics)

[sogaiu]

Looks neat!

Sorry to only have a minor comment here -- would you mind doing make format?

FWIW, the following is the diff I get currently when I do that:

diff --git a/src/core/net.c b/src/core/net.c
index 8c911f92..ac97554a 100644
--- a/src/core/net.c
+++ b/src/core/net.c
@@ -894,32 +894,32 @@ static const struct sockopt_type sockopt_type_list[] = {
 };
 
 JANET_CORE_FN(cfun_net_setsockopt,
-             "(net/setsockopt stream option value)",
-             "set socket options.\n"
-             "\n"
-             "supported options and associated value types:\n"
-             "- :SO_BROADCAST boolean\n"
-             "- :SO_REUSEADDR boolean\n"
-             "- :SO_KEEPALIVE boolean\n"
-             "- :IP_MULTICAST_TTL number\n"
-             "- :IP_ADD_MEMBERSHIP string\n"
-             "- :IP_DROP_MEMBERSHIP string\n"
-             "- :IPV6_JOIN_GROUP string\n"
-             "- :IPV6_LEAVE_GROUP string\n") {
+              "(net/setsockopt stream option value)",
+              "set socket options.\n"
+              "\n"
+              "supported options and associated value types:\n"
+              "- :SO_BROADCAST boolean\n"
+              "- :SO_REUSEADDR boolean\n"
+              "- :SO_KEEPALIVE boolean\n"
+              "- :IP_MULTICAST_TTL number\n"
+              "- :IP_ADD_MEMBERSHIP string\n"
+              "- :IP_DROP_MEMBERSHIP string\n"
+              "- :IPV6_JOIN_GROUP string\n"
+              "- :IPV6_LEAVE_GROUP string\n") {
     janet_arity(argc, 3, 3);
     JanetStream *stream = janet_getabstract(argv, 0, &janet_stream_type);
     janet_stream_flags(stream, JANET_STREAM_SOCKET);
     JanetKeyword optstr = janet_getkeyword(argv, 1);
 
     const struct sockopt_type *st = sockopt_type_list;
-    while(st->name) {
+    while (st->name) {
         if (janet_cstrcmp(optstr, st->name) == 0) {
             break;
         }
         st++;
     }
 
-    if(st->name == NULL) {
+    if (st->name == NULL) {
         janet_panicf("unknown socket option %q", argv[1]);
     }
 
@@ -932,19 +932,19 @@ JANET_CORE_FN(cfun_net_setsockopt,
     void *optval = (void *)&val;
     socklen_t optlen = 0;
 
-    if(st->type == JANET_BOOLEAN) {
+    if (st->type == JANET_BOOLEAN) {
         val.v_int = janet_getboolean(argv, 2);
         optlen = sizeof(val.v_int);
-    } else if(st->type == JANET_NUMBER) {
+    } else if (st->type == JANET_NUMBER) {
         val.v_int = janet_getinteger(argv, 2);
         optlen = sizeof(val.v_int);
-    } else if(st->optname == IP_ADD_MEMBERSHIP || st->optname == IP_DROP_MEMBERSHIP) {
+    } else if (st->optname == IP_ADD_MEMBERSHIP || st->optname == IP_DROP_MEMBERSHIP) {
         const char *addr = janet_getcstring(argv, 2);
         memset(&val.v_mreq, 0, sizeof val.v_mreq);
         val.v_mreq.imr_interface.s_addr = htonl(INADDR_ANY);
         val.v_mreq.imr_multiaddr.s_addr = inet_addr(addr);
         optlen = sizeof(val.v_mreq);
-    } else if(st->optname == IPV6_JOIN_GROUP || st->optname == IPV6_LEAVE_GROUP) {
+    } else if (st->optname == IPV6_JOIN_GROUP || st->optname == IPV6_LEAVE_GROUP) {
         const char *addr = janet_getcstring(argv, 2);
         memset(&val.v_mreq6, 0, sizeof val.v_mreq6);
         val.v_mreq6.ipv6mr_interface = 0;
@@ -957,7 +957,7 @@ JANET_CORE_FN(cfun_net_setsockopt,
     janet_assert(optlen != 0, "invalid socket option value");
 
     int r = setsockopt((JSock) stream->handle, st->level, st->optname, optval, optlen);
-    if(r == -1) {
+    if (r == -1) {
         janet_panicf("setsockopt(%q): %s", argv[1], strerror(errno));
     }
 

[zevv]

Formatting applied; seems that MacOS failed, i'll look into that.

[zevv]

Yeah, this is hard without having a mac at hand; missing some #include or magic _XOPEN_SOURCE define I guess, sigh...

[sogaiu]

No clue whether these might help, but they refer to some of the names mentioned as "undeclared identifier" in the error output:

• https://www.unix.com/man-page/osx/4/ip/
• https://opensource.apple.com/source/xnu/xnu-4570.1.46/bsd/netinet/in.h.auto.html

Chromium source had some bit that seemed related at the top of this file.

[tionis]

I think whenever keywords are used as arguments (or parts or arguments) in the stdlib they are lowercase, so perhaps this would also make sense here for consistency?

[zevv]

I think whenever keywords are used as arguments (or parts or arguments) in the stdlib they are lowercase, so perhaps this would also make sense here for consistency?

yeah, good point. I don't really have an opinion about this; upper case seemed the natural choice because of the underlying constants, but lower case is more natural to Janet. I'd be happy to change this.

[zevv]

Indeed, magic define _DARWIN_C_SOURCE was missing, thanks @disruptek

[bakpakin]

Cool, multicast was something I wanted to experiment with. Thanks for the work, @zevv and the review everyone else!

LGTM